A Novel Convex Relaxation for Non-Binary Discrete Tomography

We present a novel convex relaxation and a corresponding inference algorithm for the non-binary discrete tomography problem, that is, reconstructing discrete-valued images from few linear measurements. In contrast to state of the art approaches that split the problem into a continuous reconstruction problem for the linear measurement constraints and a discrete labeling problem to enforce discrete-valued reconstructions, we propose a joint formulation that addresses both problems simultaneously, resulting in a tighter convex relaxation. For this purpose a constrained graphical model is set up and evaluated using a novel relaxation optimized by dual decomposition. We evaluate our approach experimentally and show superior solutions both mathematically (tighter relaxation) and experimentally in comparison to previously proposed relaxations

Interorganisational Information Systems Maturity: Do Supply Chain Integration and Business/IT-Alignment Coincide?

Although interorganisational information systems (IOIS) have existed as study object for a long time, much research into IOIS remains sector-specific. By employing a multisector dataset, this paper aims to contribute to the cross-sectoral analysis of IOIS. We formulate four hypotheses on IOIS maturity based on theory concerning supply chain integration and business/IT-alignment, taking both ‘IT’ and ‘organisation’, and ‘supply’ and ‘demand’ into account. This leads to the twofold research question (i) how IOIS maturity of organisations can be measured in a generic manner, and (ii) if supply chain integration and business/IT-alignment are related as similar determinants of IOIS maturity. We empirically test our hypotheses on survey data collected among a group (n=74) of Dutch organisations, diverse in terms of industry and size. Correlation analysis confirms all four hypotheses. This indicates that business/IT-alignment and supply chain integration are indeed related

Continuum microhaemodynamics modelling using inverse rheology

Modelling blood flow in microvascular networks is challenging due to the complex nature of haemorheology. Zero- and one-dimensional approaches cannot reproduce local haemodynamics, and models that consider individual red blood cells (RBCs) are prohibitively computationally expensive. Continuum approaches could provide an efficient solution, but dependence on a large parameter space and scarcity of experimental data for validation has limited their application. We describe a method to assimilate experimental RBC velocity and concentration data into a continuum numerical modelling framework. Imaging data of RBCs were acquired in a sequentially bifurcating microchannel for various flow conditions. RBC concentration distributions were evaluated and mapped into computational fluid dynamics simulations with rheology prescribed by the Quemada model. Predicted velocities were compared to particle image velocimetry data. A subset of cases was used for parameter optimisation, and the resulting model was applied to a wider data set to evaluate model efficacy. The pre-optimised model reduced errors in predicted velocity by 60% compared to assuming a Newtonian fluid, and optimisation further reduced errors by 40%. Asymmetry of RBC velocity and concentration profiles was demonstrated to play a critical role. Excluding asymmetry in the RBC concentration doubled the error, but excluding spatial distributions of shear rate had little effect. This study demonstrates that a continuum model with optimised rheological parameters can reproduce measured velocity if RBC concentration distributions are known a priori. Developing this approach for RBC transport with more network configurations has the potential to provide an efficient approach for modelling network-scale haemodynamics

Geometric reconstruction methods for electron tomography

Electron tomography is becoming an increasingly important tool in materials science for studying the three-dimensional morphologies and chemical compositions of nanostructures. The image quality obtained by many current algorithms is seriously affected by the problems of missing wedge artefacts and nonlinear projection intensities due to diffraction effects. The former refers to the fact that data cannot be acquired over the full $180^\circ$ tilt range; the latter implies that for some orientations, crystalline structures can show strong contrast changes. To overcome these problems we introduce and discuss several algorithms from the mathematical fields of geometric and discrete tomography. The algorithms incorporate geometric prior knowledge (mainly convexity and homogeneity), which also in principle considerably reduces the number of tilt angles required. Results are discussed for the reconstruction of an InAs nanowire

Self-reported effects of online medical information on offline medical behaviour

This study shows an initial direction of research where online behaviour is linked to offline behaviour of health consumers. Although no significance where found between online medical resources, it is stipulated that people are influenced by online medical information about their (possible) diseases or symptoms. Medical care providers should be aware of consumers that are heavily using the Internet as a resource of information reflecting back to their own situation. They should not reject this information immediately, but emphasize this and guide these people to professional websites or online communities to prevent unhealthy situations. Discussing online information can only increase the knowledge of the patient, to the extent that he or she can act upon it

Does ICT Policy Improve Interorganisational ICT for SMEs? A Dutch Policy Evaluation Study

Interorganisational ICT has become critical for the performance of both small and large organisations. SMEs however, traditionally lag behind in the uptake of these systems. In many countries, various policy programmes are initiated to improve ICT uptake by SMEs and support them in digital linking throughout their value chain. In the Netherlands, a nationwide policy programme was in place between 2002 and 2007 that is a prominent example of this type of policy initiatives. In this paper we present the results of an ex post evaluation of this programme, by comparing survey data collected among 516 participating SMEs with survey data collected among a control group of 124 SMEs. In bivariate analysis, significant differences are found between the two groups with regard to the adoption of several types of interorganisational ICT. These differences remain intact if split sampling of the groups is applied by size (small/medium) and sector (trade/finance/public). Furthermore, it is found that participants of the policy programme perceived significantly more added value of ICT. In interpreting these results however, pre-selection effects should be taken into account

Contribution of orbital forcing and Deccan volcanism to global climatic and biotic changes across the Cretaceous-Paleogene boundary at Zumaia, Spain

Untangling the timing of the environmental effects of Deccan volcanism with respect to the Chicxulub impact is instrumental to fully assessing the contributions of both to climate change over the Cretaceous-Paleogene boundary (KPB) interval. Despite recent improvements in radiometric age calibrations, the accuracy of age constraints and correlations is insufficient to resolve the exact mechanisms leading to environmental and climate change in the 1 m.y. across the KPB. We present new high-resolution planktic foraminiferal, geochemical, and geophysical data from the Zumaia section (Spain), calibrated to an updated orbitally tuned age model. We provide a revised chronology for the major carbon isotope excursions (CIEs) and planktic foraminiferal events and test temporal relationships with different models of the eruptive phases of the Deccan Traps. Our data show that the major CIEs near the KPB, i.e., the late Maastrichtian warming event (66.25–66.10 Ma) and the Dan-C2 event (65.8–65.7 Ma), are synchronous with the last and the first 405 k.y. eccentricity maximum of the Maastrichtian and the Danian, respectively, and that the minor Lower C29n event (65.48–65.41 Ma) is well constrained to a short eccentricity maximum. Conversely, we obtained evidence of abrupt environmental change likely related to Deccan volcanism at ca. 65.9 Ma, based on a bloom of opportunistic triserial guembelitriids (Chiloguembelitria). The orbital, isotopic, and paleobiological temporal relationships with Deccan volcanism established here provide new insights into the role of Deccan volcanism in climate and environmental change in the 1 m.y. across the KPB. © 2021. The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license

Chain Digitisation Maturity and Its Determinants: A Dutch CIO Survey and Case Study

Interorganisational or chain information systems have become a frequent subject of scientific research, but not often an empirical perspective on these systems is taken. In this study we develop a model for measuring the chain digitisation maturity of organisations and validate it by conducting a survey among 33 CIOs. In addition, one of the responses is further investigated through a case study. Based on the survey data, three determinants, namely (i) complexity of chain digitisation solutions, (ii) synchronisation of data and (iii) the size of the organisation, appear to be correlated with chain digitisation maturity. This is confirmed by the case study, which also provides a deeper understanding of alignment of technology and organisation on the one hand, and the supply and demand chain partners on the other. We conclude that the topic of chain digitisation alignment deserves further research, as does its situationality for profit and non-profit organisations

A parametric level-set method for partially discrete tomography

This paper introduces a parametric level-set method for tomographic reconstruction of partially discrete images. Such images consist of a continuously varying background and an anomaly with a constant (known) grey-value. We represent the geometry of the anomaly using a level-set function, which we represent using radial basis functions. We pose the reconstruction problem as a bi-level optimization problem in terms of the background and coefficients for the level-set function. To constrain the background reconstruction we impose smoothness through Tikhonov regularization. The bi-level optimization problem is solved in an alternating fashion; in each iteration we first reconstruct the background and consequently update the level-set function. We test our method on numerical phantoms and show that we can successfully reconstruct the geometry of the anomaly, even from limited data. On these phantoms, our method outperforms Total Variation reconstruction, DART and P-DART.Comment: Paper submitted to 20th International Conference on Discrete Geometry for Computer Imager

Molecular Mechanics and SCF MO Conformational Analysis of Indol-3-ylacetic Acid Phytohormone (Auxin)

Conformational analysis of indol-3-ylacetic acid (IAA)-plant growth hormone has been performed using molecular mechanics and the ab initio SCF MO theory. The equilibrium geometry of IAA has been determined. Relative energies of alternative conformations, their charge distribution, dipole moment and energy barriers between them have been calculated. The position of the carboxyl group relative to the indole ring depends on two torsion angles, Tl(C2-C3-C8-C9) and T2(C3-C8-C9=02). Rotational barriers for these two angles were explored and it emerged that both rotations (about the C3-C8and C8-C9 bonds) can be accomplished in a reasonable time period at room temperature (the barrier height is about 4.6-10.9 (TI) and 1.7-3.8 (T2) kJ/mol respectively, according to ab initio calculations. Ab initio (GAMESS)and molecular mechanics (DISCOVER (CVFF and cff91), SYBYL(TRIPOS) and MM2(87), calculations revealed qualitatively the same shape of potential energy surface (E =f(Tl, T2)). However, energy differences between various conformations depend on the basis set (ab initio calculations) and force field (molecular mechanics) used